1. Field of the Invention
The present invention relates to a method of making a multiple layer substrate with at least one layer of a carrier substrate comprising synthetic fibers and at least one layer of an air laid material layer comprising natural fibers wherein the carrier substrate and air laid material layer are hydroentagled together to form an integrated substrate. Another aspect of the present invention, in the formation of a low-density cleaning substrate with a basis weight of less than 100 gsm, or less than 80 gsm, or less than 50 gsm which may be expanded in the z-direction to give the consumer the appearance of additional perceived bulk and thickness. The cleaning substrate comprises at least one layer of a carrier web and at least one layer comprising an air laid cellulosic material.
One embodiment of the invention, is the method of forming a dual layer substrate of carrier material and cellulosic material consists of the following steps:
(a) depositing a carrier web onto a forming screen, (b) air laying a layer of cellulosic material on top of the carrier web; (c) subjecting the intermediate substrate layers to a water curtain to saturate the cellulosic material with water; (d) hydroentangling the carrier web and air laid layer together to form a fully bonded dual layer substrate. The present invention further relates to cleaning substrates that are preferably used as wipes for delivering cleaning, disinfecting and surface protective compositions to both hard and soft surfaces. The cleaning substrate may be a pre-loaded cleaning wipe preferably comprised of non-woven materials.
2. Description of Related Art
A variety of liquid and solid or semi-solid ingredients have been deposited onto various forms of substrates for a variety of purposes. Typically, the substrates are wipes, formed of either a woven or non-woven material, and containing a liquid active composition. In one form, a non-woven material is soaked in a liquid cleaning active, and packaged in a canister. One example of this form of a disposable cleaning wipe is a product manufactured and sold by the Clorox Company under the trademark Clorox® Disinfecting Wipes.
Cleaning wipes have long been used for a variety of purposes. Such cleaning wipes have contained various compounds to accomplish their intended purpose. Cleaning wipes have included soaps and detergents to clean hard surfaces such as tiles, ceramics, counter tops, floors, and the like, as well soft surfaces such as fabrics and upholstery. Wipes have been formulated with personal care products, for example to clean an individual's hands. Cleaning wipes have also included ammonia to clean glass surfaces. Alcohol and various other biocides, such as quats, and biguanides have been included on cleaning wipes to disinfect a variety of surfaces. Cleaning wipes have also included waxes to polish and clean furniture.
All of the foregoing examples are limited in at least one or more of the following ways. First, many of the wipes or substrates have a basis weight of greater than 100 gsm because higher basis weight substrates are customarily used because of their ability to effectively absorb and hold cleaning compositions. Secondly, many of the existing wipes are flat and consumers have traditionally rejected flat, low basis weight cleaning wipes and substrates because they appear too flimsy or thin to effectively clean surfaces. Thirdly, many of the existing cleaning substrates which comprise meltblown and/or spunbond layers and cellulosic layers of pulp material require that the pulp layer be positioned in between two layers of meltblown or spunbond material layers or that the pulp layer be wetlaid or foam laid onto another layer of substrate material.
Hydroentangling or spunlacing is a technique introduced during the 1970's, see e.g. CA patent no. 841 938. The method involves forming a fiber web which is either drylaid, wetlaid, or carded after which the fibers are entangled by means of very fine water jets under high pressure. Several rows of water jets are directed against the fiber web which is supported by a movable wire. The entangled fiber web is then dried. The fibers that are used in the material can be synthetic or regenerated staple fibers, e.g. polyester, polyamide, polypropylene, rayon or the like, pulp fibers or mixtures of pulp fibers and staple fibers. Spunlace materials can be produced in high quality to a reasonable cost and have a high absorption capacity. They can e.g. be used as wiping material for household or industrial use, as disposable materials in medical care and for hygiene purposes etc.
Through e.g. EP-A-0 333 211 and EP-A-0 333 228 it is known to hydroentangle a fiber mixture in which one of the fiber components is meltblown fibers. In these patents, the meltblown fiber adheres to other fibers in the substrate material to form a base material. The base material, i.e. the fibrous material which is exerted to hydroentangling, either consists of at least two preformed fibrous layers where one layer is composed of meltblown fibers or of a “coform material” where an essentially homogeneous mixture of meltblown fibers and other fibers. These patents do not describe a process of forming a separate synthetic carrier web material and then subsequently forming an air laid layer comprising natural fibers where the layers are combined solely by hydroentangling. The process described by EP-A-0 333 211 and EP-A-0 333 228 require that the meltblown or coform materials trap or bond to any additional fibrous materials components so that the resulting substrate is bonded together by the meltblown or coform process in addition to the hydroentangling process.
U.S. Pat. No. 7,422,660 to Billgren, et al. is directed to a process for forming a nonwoven material comprising the steps of: (1) forming a continuous filament web; (2) wetting the continuous filament web; (3) wet laying or foam laying a layer of staple fibers comprising natural and/or synthetic fibers on top of the continuous formed filament web; and (4) hydroentangling the continuous filament web and the layer of staple fibers. The process of Billgren forms a nonwoven substrate of spunlaid or meltblown continuous filaments hydroentagled with a layer of synthetic and/or natural fibers which is wetlaid or foam laid. Since this invention only describes a process and substrate which may have natural fibers which are wet laid or foam laid, not air laid.
U.S. Pat. No. 7,410,683 to Curro, et al. describes a laminate web material comprising two discrete material webs of tufted material which are laminated together to form a patterned/tufted substrate. This patent refers to a wide variety of methods for forming textured webs including thermoforming, applying high-pressure plates or rolls, hydraulic forming, casting and embossing. This patent teaches the use of lamination and various texturing and patterning techniques, it does not employ a hydroentangling process to make the layers form an integrated substrate.
U.S. Pat. No. 6,163,943 to Johansson, et al. describes a method for producing a nonwoven material by hydroentagling a mixture of continuous filaments and natural fibers. In Johansson's process, a layer of continuous filaments is formed into a layer of material and then a second layer of foamformed material comprising natural fibers is formed, the two layers are hydroentangled together to form a substrate. The foamforming process described in Johnsson's invention requires that the fibrous web is formed from a dispersion of fibers in foamed liquid containing water and a tenside. The foamformed layer of material must be then drained through the filament layer to remove the excess liquid prior to hydroentangling the two layers together to form an integrated substrate. The process described in Johansson has the advantages of forming a well integrated substrate of continuous filaments and natural fibers which exhibits very good strength properties and absorption at basis weights of less than 100 gsm. The disadvantages of a substrate formed by this process are that the foamforming step of the process requires expensive and equipment which is not available at wide variety of nonwoven suppliers and the process requires a step of draining the foam formed material prior to hydroentangling the substrate materials.
U.S. Pat. No. 6,762,138 to Ferreira, et al. describes a multilayer a layer of wet-laid nonwoven web comprising pulped natural fibers and layer of synthetic fibers which are hydroentangled together to form a composite multilayer material. The process described by Ferreria, requires that the layer of natural pulp and unpulped fibers be formed by a wet papermaking process, which involves forming a fluid dispersion of the fibers and collecting the fibers on a fiber collecting wire to form a continuous sheet web material. The substrates described by Ferreria have a basis weight of about 60 to 160 gsm. Although the substrates described by Ferreria have the advantages of being strong, absorbent, with relatively low basis weights, they suffer from the disadvantage of requiring a wet laid process which involves expensive papermaking machines required for creating wet laid materials. The invention of Ferreria only teaches a substrate and method for forming single or multilayer substrates using wet-laid natural fibers.
In view of the present state of the art of non-woven substrates such as cleaning wipes, there remains a need for a low basis weight, non-woven substrate comprising air laid natural fibers and synthetic fibers which are hydroentangled to form an integrated substrate material. In addition, it is desirable to have a process for forming multiple layer hydroentangled substrates of natural and synthetic fibers which does not require wet laid natural fibers and the expensive processing machines required to form wet laid material layers.